Prior art devices for controlling the matching of an rf load to an rf source generally include detectors for various parameters of the load and/or relationships of differential characteristics between the source and load. Typical of these detectors are sensors for resistance, conductance, impedance magnitude, voltage standing wave ratio (VSWR) and differential phase between the source and load. Output signals from these detectors are supplied to a control network for impedances of a matching network between the rf source and rf load. Usually, the control network varies the values of the impedances, which in turn causes output signals from the detectors to vary or toggle about pre-establish levels therefor. There is thus derived an indication of whether the detected parameter, for a particular operating frequency of the source, is above or below the pre-established level. Matching is achieved when the detected parameters are at the pre-established levels.
While these prior art matching devices are generally satisfactory, they have certain disadvantages. In particular, the detectors employed in the prior art matching apparatus are frequently difficult to fabricate and adjust. If the rf source has wide power and frequency ranges, such as 30 dB and 2-30 megaHertz respectively, the cost and time to fabricate and adjust the detectors and coupling networks associated therewith are extensive. Because of these cost and time factors, the typical prior art device has a relatively limited rf dynamic power range. Each detector often requires several watts of transmitted rf power, which can be particularly deleterious for mobile, e.g., "manpack" applications. Each of the detectors employed with the prior matching devices usually has a specialized output signal, tailored to a particular application. The detectors associated with a particular matching apparatus often cannot be used if the impedance of the load being matched varies over a wide range of values.
It is, accordingly, an object of the present invention to provide a new and improved apparatus for and method of determining and controlling the match of an rf load to an rf source.
Another object of the invention is to provide a new and improved rf matching apparatus that is relatively easy to fabricate and adjust because the need for specialized detectors is obviated.
Still another object of the present invention is to provide a new and improved rf matching apparatus and method that can be employed over wide frequency and rf power levels.
Still a further object of the present invention is to provide an rf matching apparatus and method that can be employed for a load susceptible of varying over a wide range of values.
Still another object of the present invention is to provide a new and improved automatic rf matching apparatus wherein the need for separate detectors for individual parameters, such as load resistance, conductance, impedance magnitude, voltage standing wave ratio and phase difference between source and load, is obviated because plural signals representing the load complex reflection coefficient are derived.